This invention relates to an apparatus for navigating a vehicle in accordance with a course set before travel starts. More particularly, the invention relates to a course guidance system in a navigation apparatus which informs a driver of characterizing features encountered along the course.
Recent years have seen extensive development of vehicular navigation systems in which a course is preset before travel starts and the driver is given course information in accordance with the preset course.
When the driver is guided along the preset course, the conventional navigation apparatus displays a map or the screen of a CRT and superimposes the course on the map.
Also, in an application filed separately by the present applicant in Japan on Feb. 27, 1987, as Patent Application No. 62-44796, there is disclosed a system in which information relating to an intersection at which the next turn is to be made is indicated to the driver by a CRT screen and voice tracks in accordance with the preset course. In this system, a photograph and the name of the intersection at which the next turn is to be made, the distance to this intersection and the shape thereof, and whether a right or left turn is to be made are displayed on the CRT screen. Together with this visual indication, the distance to the intersection and the direction of advance from this intersection are announced by voice tracks.
With the former prior-art arrangement in which the map and the superimposed course are displayed, a characterizing feature serving as a landmark in the vicinity of the present position of the vehicle is read, and it is necessary that the driver determine where his present travelling position is on the map and how far it is to a specific intersection. However, a highly detailed display cannot be presented on a small CRT of the type mounted in an automotive vehicle, and it is very difficult for the driver to read all of the necessary information while driving. Consequently, considerable attention must be paid in recognizing intersections and, hence, a great burden is placed upon the driver.
With the latter arrangement in which intersection information is outputted on the CRT screen and by voice track, no course guidance is given until the vehicle has approached the vicinity of an intersection. Consequently, if the distance between one intersection at which a turn has been made and an intersection at which the next turn is to be made is great, the driver cannot verify whether the course presently being travelled on is correct, and the driver is constrained to drive the vehicle while constantly in an anxious state until the intersection requiring a turn is reached.